Research On Performance Optimization Method Of Switched Reluctance Motor Drive System

The research topic in this thesis is an important part of the Natural Science Foundation of Shanxi Province “Research on Mutual Inductance of Switched Reluctance Motor and Its Influence on Torque”(Serial Number:110148032).The switched reluctance motor(SRM)has advantages of wide speed range,reliable operation,excellent starting performance and high efficiency due to its special structure.It has a good application prospect,and has been widely studied at home and abroad.However,in the aspect of nonlinear control strategy,it is necessary to further study the design of the controller to realize the cost and control effect.SRMs have high operating efficiency,but the advantage of efficiency needs to be combined with the appropriate control strategy.There is poor load capacity with SRM in high speed operation.In order to enhance the market competitiveness of SRMs,it is of great practical significance to study the optimization control methods of SRM.Problems of the existing system in nonlinear control technology are cleared through literature review,research and other methods.Therefore,a three-phase switched reluctance motor,with the stator and the rotor for 12/8 poles and the power for 7.5kW,is used for research in this thesis.Committed to improving its performances from the control point of view,and the control methods of SRM are studied comprehensively and deeply.The specific research contents of this thesis are as follows.On the basis of the original control circuit,the hardware circuit of the new system with TMS320F28335 as the control core is designed and perfected,which includes current signal detection and conditioning circuit,rotor position signal detection and conditioning circuit,serial communication circuit,etc.The new switched reluctance drive system application program,which is programmed by C language,include smoothly starting subroutine,the commutation subroutine,the speed calculation subroutine,the control mode subroutine,the communication subroutine,the fault protection subroutines such as the current protection subroutine and the overload protection subroutine,etc.Nonlinear inductance profiles of SRM cause the complicated design of controller,which makes SRMs not widely used in industries.A traditional fixed gain PI controller is easily implementable but insufficient to give good control performance over the whole range of operation.To solve the problem,this thesis designs an easily implementable gain-scheduling PI speed controller based on the characteristics of SRM,the output of the speed regulator is used as the reference current or the duty cycle depending on the actual speed of motor.A first-order dynamic model of SRM in s domain is derived,which is useful for gain-scheduling control.The relationship between PI parameters,average voltage and actual speed of the system is obtained.The adaptive adjustment of PI parameters is realized.A traditional PI controller and the gain-scheduling PI controller have been compared by experiments,the results show that a high performance is achieved when adopting the variable gain PI controller.The system has rapid response with little overshoot and high robustness to load torque disturbance,the steady state error is zero.The inherent nonlinearity,saturation and coupled magnetization of SRM make it hard to get a good performance by using the conventional analytical method.This thesis proposes an easily implementable method to model the SRM based on the characteristics of nonlinear inductance.Taking a three-phase,12/8-pole SRM as an example,the inductance parameter of the SRM is obtained by finite element simulation.Considering the back electromotive force,the computational model of optimal turn-on angle based on the non-linear model of inductance in the low-inductance region is established.The computational model of optimal turn-off angle is derived from the turn-on angle and the variation law of flux-linkage.According to operating conditions of the SRM,the adaptive adjustment of turn-on angle and turn-off angle is realized.The experimental results show that the proposed method of switching angle optimization is simple and efficient,which can improve the operating efficiency of SRM.The existing excitation method can only be used in the low speed range.This thesis presents a simple and practical single-double-phase excitation method,which is especially suitable for high speed operation of SRM.The improved single-double-phase excitation method is theoretically analyzed based on torque-angle characteristics of the SRM,and realized by software programming.The control performances of the single phase excitation method and the improved single-double-phase excitation method are compared by experiments.The experimental results show that the improved single-double-phase excitation method improves the load carrying capacity of SRM at high speed.